A high pressure discharge lamp with a discharge vessel of quartz has been widely used as a head light for an automobile due to its high brightness and light emission efficiency. The discharge vessel has a light emitting portion and contains a light emitting gas inside of the vessel. The discharge vessel of such discharge lamp is made of quartz and thus transparent, so that the light emitting portion may function as a point light source.
Japanese patent publication 5-8684A (8684A/1993) disclosed a head lamp for an automobile having a combination of a metal halide lamp and a high pressure sodium lamp as light sources for the head lamp.
The assignee filed a Japanese patent publication 2001-76677A, and disclosed a high pressure discharge lamp usable as a pseudo point light source for an automobile head lamp. According to the description in the publication, when a light emitter is contained within a light emitting vessel made of quartz and powered, the inner light emitter in the transparent quartz vessel may be shown from the outside of the vessel. The light emitter thereby functions as a point light source. On the contrary, a high pressure discharge lamp using a vessel of a translucent polycrystalline alumina is semitransparent, so that the whole of the vessel functions as an integral light emitter when observed from the outside of the vessel. It is thereby necessary to sufficiently miniaturize the light emitting vessel itself so that the vessel may function as a pseudo point light source.
For example in a head lamp for an automobile, a light emitting vessel is set on a predetermined position. Light emitted from the vessel is then reflected by a reflector to project the reflected light forwardly. The relationship of three dimensional positions of the point light source and reflector, as well as the surface shape of the reflector, are accurately determined, so as to avoid a reduction of condensing efficiency at a focal point.
As described above, the relationship of three dimensional positions of the point light source in the discharge lamp (or the pseudo point light source) and the reflector should be accurately determined. The method of fixing the discharge lamp with respect to the reflector substrate thus becomes problematic.
For example, Japanese utility model application 6-64201A discloses a method of fixing as shown in FIG. 1. That is, a through hole 7 for fixing an electrode and a setting hole 11a for fixing a discharge lamp are provided in a reflector substrate 11 composed of a ceramic.
When a luminous vessel 5 is fixed at a specific position with respect to the reflector substrate 11, one end of the luminous vessel 5 is inserted into a setting hole 11a. At this stage, the end part 5a and a power supply member 2A pass through the setting hole 11a and protrudes to the side of the convex of the reflector substrate 11. A metal jig 22 for power supply is provided to the tip end of the end part 5a, and the metal jig 22 protrudes to the outside of the reflector substrate 11. Further, a power supply member 20 is mechanically fixed and electrically connected to a power supply member 6 intersecting the same. The tip end of the power supply member 6 is inserted into a through hole 7 of the reflector substrate 11. The luminous vessel 5 is then positioned.